/*
自己选择的路 ,跪着也要走完。朋友们 , 虽然这个世界日益浮躁起来,只
要能够为了当时纯粹的梦想和感动坚持努力下去 , 不管其它人怎么样,我
们也能够保持自己的本色走下去。
To the world , you will be a person , but to a person , you
will be the world .                               ——AKPower
*/
//作者:AKPower
//算法:
#include <iostream>
#include <cmath>
#include <algorithm>
#include <cstring>
#include <vector>
#include <map>
#include <queue>
#include <cstdio>
#include <string>
#include <stack>
#include <set>
#define IOS ios::sync_with_stdio(false), cin.tie(0)
using namespace std;
typedef long long ll;
const int maxn = 1e5 + 10;
int d[maxn];
vector<int> ve[maxn];
int dp[maxn];
int n, m;

struct node
{
    int x, du;
    bool operator<(const node &t) const
    {
        return du < t.du;
    }
} a[maxn];

int main()
{
    IOS;
    cin >> n >> m;
    memset(d, 0, sizeof(d));
    for (int i = 0; i < m; i++)
    {
        int x, y;
        cin >> x >> y;
        d[x]++, d[y]++;
        ve[x].push_back(y);
        ve[y].push_back(x);
    }

    for (int i = 0; i < n; i++)
    {
        a[i].x = i, a[i].du = d[i];
        dp[i] = 1;
    }

    sort(a, a + n);

    for (int i = 0; i < n; i++)
    {
        int x = a[i].x, du = a[i].du;
        for (int i = 0; i < ve[x].size(); i++)
        {
            int y = ve[x][i];
            if (d[y] > du)
                dp[y] = max(dp[y], dp[x] + 1);
        }
    }
    int ans = 0;
    for (int i = 0; i < n; i++)
        ans = max(ans, dp[i]);
    cout << ans;
    getchar();
    getchar();
    return 0;
}
